Well, one possible outcome could be that Naruto and Sasuke manage to defeat Madara through their combined strength and newfound powers. They might use their signature jutsus in a coordinated way that Madara can't counter.
In such a fanfiction, Naruto and Sasuke might win. They are both extremely powerful and their combined strength, like Naruto's Rasengan and Sasuke's Chidori, could overpower Madara.
Sasuke could also be the one. With his Sharingan and Rinnegan, he has unique abilities. He might use his Amaterasu in a very unexpected way, like creating a large - scale trap for Madara using the black flames. His intelligence and cold - blooded nature in battle make him capable of making a decisive move.
Sasuke is often a popular character in these fanfictions. He might play a role in helping Naruto against Madara or have his own motives during their battle. Kakashi can also be a prominent figure, perhaps using his Sharingan in a crucial moment to assist Naruto. Another popular character could be Hashirama, as his connection to Madara is a key part of the original story and can be further explored in fanfiction.
Another theme is redemption. Sometimes in these fanfics, Madara has a chance at redemption through his fight with Naruto. Naruto's belief in people's goodness can influence the outcome in such scenarios.
She could try to appeal to Sasuke's emotions. If she can remind him of their past, of the times they fought together and cared for each other, it might make him release her. Sakura could talk about their shared experiences and how they are on the same side deep down, hoping to break through whatever is making Sasuke hold her captive.
The abilities might be different too. Since Naruto has his own set of skills like the Rasengan and Sage Mode, his Susanoo could incorporate those elements. For example, his Susanoo's hands could form giant Rasengan - like attacks, or it could have the ability to enter Sage Mode, which would be a huge departure from the regular Uchiha Susanoo's abilities.
One possible fanfiction could be about Sasuke using his Susanoo to save Sakura from a dangerous enemy. In this scenario, Sasuke, seeing Sakura in peril, quickly activates his Susanoo. The powerful, spectral form of the Susanoo reaches out with its massive hand and grabs Sakura, pulling her to safety. This moment could be a turning point in their relationship, with Sakura realizing anew how much Sasuke still cares for her, despite their past differences.
Naruto would probably win. He has an indomitable will and has always found ways to overcome powerful foes. His experience and the unique powers he might gain with the Rinnegan could give him an edge over Madara.